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Commit 934e6ebf authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
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tty: Redo current tty locking 



Currently it is sometimes locked by the tty mutex and sometimes by the
sighand lock. The latter is in fact correct and now we can hand back referenced
objects we can fix this up without problems around sleeping functions.

Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2cb5998b

drivers/char/tty_io.c

+4 −14
Original line number Diff line number Diff line
@@ -739,13 +739,11 @@ void tty_vhangup_self(void) 
{

	struct tty_struct *tty;



	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	if (tty) {

		tty_vhangup(tty);

		tty_kref_put(tty);

	}

	mutex_unlock(&tty_mutex);

}



/**
@@ -801,11 +799,9 @@ void disassociate_ctty(int on_exit) 
	struct pid *tty_pgrp = NULL;





	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	if (tty) {

		tty_pgrp = get_pid(tty->pgrp);

		mutex_unlock(&tty_mutex);

		lock_kernel();

		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)

			tty_vhangup(tty);
@@ -822,7 +818,6 @@ void disassociate_ctty(int on_exit) 
			kill_pgrp(old_pgrp, SIGCONT, on_exit);

			put_pid(old_pgrp);

		}

		mutex_unlock(&tty_mutex);

		return;

	}

	if (tty_pgrp) {
@@ -837,7 +832,6 @@ void disassociate_ctty(int on_exit) 
	current->signal->tty_old_pgrp = NULL;

	spin_unlock_irq(&current->sighand->siglock);



	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	if (tty) {

		unsigned long flags;
@@ -854,7 +848,6 @@ void disassociate_ctty(int on_exit) 
		       " = NULL", tty);

#endif

	}

	mutex_unlock(&tty_mutex);



	/* Now clear signal->tty under the lock */

	read_lock(&tasklist_lock);
@@ -3180,14 +3173,11 @@ static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty) 
struct tty_struct *get_current_tty(void)

{

	struct tty_struct *tty;

	WARN_ON_ONCE(!mutex_is_locked(&tty_mutex));

	unsigned long flags;



	spin_lock_irqsave(&current->sighand->siglock, flags);

	tty = tty_kref_get(current->signal->tty);

	/*

	 * session->tty can be changed/cleared from under us, make sure we

	 * issue the load. The obtained pointer, when not NULL, is valid as

	 * long as we hold tty_mutex.

	 */

	barrier();

	spin_unlock_irqrestore(&current->sighand->siglock, flags);

	return tty;

}

EXPORT_SYMBOL_GPL(get_current_tty);

drivers/s390/char/fs3270.c

+1 −0
Original line number Diff line number Diff line
@@ -431,6 +431,7 @@ fs3270_open(struct inode *inode, struct file *filp) 
		tty = get_current_tty();

		if (!tty || tty->driver->major != IBM_TTY3270_MAJOR) {

			tty_kref_put(tty);

			mutex_unlock(&tty_mutex);

			rc = -ENODEV;

			goto out;

		}

fs/dquot.c

+0 −2
Original line number Diff line number Diff line
@@ -895,9 +895,7 @@ static void print_warning(struct dquot *dquot, const int warntype) 
	    warntype == QUOTA_NL_BSOFTBELOW || !need_print_warning(dquot))

		return;



	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	mutex_unlock(&tty_mutex);

	if (!tty)

		return;

	tty_write_message(tty, dquot->dq_sb->s_id);

security/selinux/hooks.c

+0 −2
Original line number Diff line number Diff line
@@ -2121,9 +2121,7 @@ static inline void flush_unauthorized_files(struct files_struct *files) 
	long j = -1;

	int drop_tty = 0;



	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	mutex_unlock(&tty_mutex);

	if (tty) {

		file_list_lock();

		file = list_entry(tty->tty_files.next, typeof(*file), f_u.fu_list);